1. Field of the Invention
The present invention relates to curable resinous compositions. More specifically, the present invention relates to novel polymers, particularly acrylic polymers useful in preparing resinous compositions which are suitable for use in coating applications, particularly cationic electrodeposition.
2. Brief Description of the Prior Art
It is known in the art that resinous materials, such as acrylic resinous materials can be solubilized in water, using cationic solubilizing groups such as amine salt groups. Such resinous materials can be used as binders for water-based coating compositions which can be deposited on substrates by flow, dip, spray and roll coating as well as by cationic electrodeposition.
Unfortunately, the art-known cationic solubilizing groups are limited in scope. This is all the more so for acrylic polymers in that they are generally derived from a limited group of amine-containing monomers or from glycidyl (meth)acrylate, the latter being reacted with amine after polymerization. Such monomers are relatively expensive, and some are of limited availability. Moreover, resins solubilized with such monomers characteristically having the following disadvantages: the presence of the amino nitrogen in the film causes discoloration of white and pastel coatings, inhibits oxidative cure and gives the coating a basic character which inhibits acid-catalyzed cures such as with aminoplast crosslinking agents.
These disadvantages have been overcome by using amine solubilizing groups which cleave and volatilize during curing. Such a technique is shown in U.S. application Ser. No. 937,386 filed Aug. 28, 1978 assigned to PPG Industries which discloses resinous compositions in which the amine solubilizing groups are incorporated into the resin via a Michael addition reaction; the amines used therein are volatile under curing conditions, i.e. at an elevated temperature, the amine is cleaved from the resin and volatilizes. An example of the resinous compositions disclosed in the above mentioned patent application are acrylic polyols transetherified with unsaturated compounds such as N-(alkoxymethyl)acrylamide to give polymers with pendant unsaturation which are capable of a Michael addition reaction with a primary or secondary amine.
The present invention provides novel polymers and amine-containing resinous compositions which are free of the afore-described disadvantages. Moreover, the present invention provides an inexpensive means of preparing amine-containing acrylic resinous compositions.